February 26-28, 2019

Colorado Convention Center
Denver, CO

Timothy MattesAssociate ProfessorThe University of Iowa

Prof. Mattes received his Bachelor’s in Civil Engineering from The Johns Hopkins University in 1994, and his Master’s in Geography and Environmental Engineering from The Johns Hopkins University in 1995. After working for 3 years as a practicing engineer designing water and wastewater facilities, he returned to graduate school in 1998. In 2004, he received a PhD in Civil and Environmental Engineering from Cornell University working with Prof. James Gossett. Since 2004, Tim has been a faculty member in the department of Civil and Environmental Engineering at The University of Iowa, and is currently an Associate Professor. His research focuses on bioremediation of toxic compounds such as vinyl chloride, PCBs, and explosives. He specializes in applying molecular biology tools and techniques to track the presence and activity of microorganisms mediating biodegradation of toxic compounds in the environment.

Typically, the desired end product of a bioremediation strategy involving in situ anaerobic reductive dechlorination of chloroethenes in groundwater plumes is ethene. However, it is well-known that the final step in the process – the reduction of vinyl chloride (VC) to ethene - is often slow under field conditions and leads to the accumulation of significant amounts of VC. However, VC and ethene production by anaerobic bacteria in groundwater systems has the potential to provide an ecological niche for aerobic ethene-oxidizing bacteria (aka etheneotrophs) even in groundwater that is considered anoxic or anaerobic. This is because etheneotrophs can operate at very low oxygen concentrations, co-metabolize VC in the presence of ethene, and even adapt to VC as a growth substrate. The process of VC oxidation by etheneotrophs therefore represents a viable supporting approach to dealing with the VC accumulation issues.

We have been investigating the ecology of VC-oxidizing etheneotrophs at several VC-contaminated sites. Using a quantitative PCR (qPCR) method that targets key etheneotroph functional genes (and their transcripts via reverse transcription (RT)-qPCR) we have observed a positive relationship between the abundance and activity of etheneotrophs and VC concentration as well as with bulk VC attenuation rates at contaminated sites. Interestingly, there was no apparent relationship between etheneotroph abundance and activity (and bulk VC attenuation rate) and dissolved oxygen (DO) concentrations. The data suggests that etheneotrophs play a major role in VC biodegradation in anoxic groundwater plumes, but that field DO measurements are not reliable predictors of active aerobic VC biodegradation processes. Because both aerobic and anaerobic VC-degrading bacteria were present and active in groundwater samples, future efforts will focus on determining spatial relationships of VC-degrading bacteria with biogeochemical parameters in cryo-core samples from a VC-contaminated site. Overall, our data indicate that practitioners interested in mitigating groundwater VC contamination via monitored natural attenuation should incorporate methods to track the abundance and activity of etheneotrophs as an integral aspect of their remediation strategy.